/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution
{
public:
    TreeNode *sortedArrayToBST(vector<int> &nums)
    {
        return sortedArrayToBST(nums, 0, nums.size());
    }

    TreeNode *sortedArrayToBST(vector<int> &nums, int beginIndex, int endIndex)
    {
        if (beginIndex == endIndex)
        {
            return nullptr;
        }
        int midIndex = (beginIndex + endIndex) / 2;
        TreeNode *tree = new TreeNode(nums[midIndex]);
        tree->left = sortedArrayToBST(nums, beginIndex, midIndex);
        tree->right = sortedArrayToBST(nums, midIndex + 1, endIndex);
        return tree;
    }
};